A lot of my collection is currently tropical non-ethnogens, so some of this information may not be quite fully applicable for your purposes.
With any propagation chamber the main issue is going to be height. Seed starter 10x20s commonly come with short-style humidity domes around 4" tall. It's difficult to use this for anything other than seedlings or small vining-type plants. They're cheaply made and unless you take good care of them, won't last more than a season or two. This style is very common, and you can find these at any Walmart, Amazon, etc. They cost around 5$
The next step up, and a bit tougher to find, is tall domes for 10x20s. They're about twice the height of the short cheapo ones and cost around 8$ for the dome only. They are slightly oversized but will fit any 10x20 out there. The build quality is a step up from the cheap ones, and they come with built in vents at both ends, and one at the top. They're nice enough to be worth using as a starting point over the short-domed ones, even though a tray/dome setup will run about double what the shorties go for. They seem a little more durable, and if not abused I could totally see them lasting 3+ seasons. I can't say for sure though, as this is my first season using them.
The next step up from the 8" domes is a stackable domed propagator made by 'earlygrow'. They're quite a bit more expensive than the previous two, but the build quality reflects the difference in price. They run around 60-80$ on amazon, and I haven't found them for sale anywhere else. They are much more of a permanent installation and could easily last 10-15+ years if taken care of. The tray is much thicker heavy duty, it's expandable, and the sections have 'heavy duty' vents on both ends, and 2 on the top cap. It has clips which hold all the seconds together, and plastic bolts which hold the sectional sides/ends. Each section is around 5-6 inches tall, and the 3-section version extends to around 18" above the top of the tray. One could comfortably fit 30+ propagations in it. I just received my first one this past week as you know, and I am absolutely in love with it. If you have the extra coin, then they are absolutely worth getting over the cheapo ones. I'll be switching my entire collection over to them eventually.
Now on to the big chambers. This is where things get expensive. You could go DIY as you already are, and that's probably the cheapest option. A 55-gallon tank runs 55$ during Petco's dollar per gallon sale, and last time I checked plexiglass can be a little pricey but isn't horrible. Correct me if I'm wrong, but maybe 20-30$ ish to retrofit a piece the approx. dimensions of a 55g lid. The great thing about a 55g is that you can put it upright on it's end to use as a makeshift greenhouse more so than a prop box.
Ikea makes some absolutely gorgeous greenhouse cabinets, but they're pricey as hell so I'm hesitant to buy one. They're basically a coated wire rack with a plexi outer shell. Looks pretty, but for 200$ they can keep it. lol One could pretty easily build one. I can't speak towards durability or their build quality, but I've seen them in person and they're suuuuper cute. haha
An MJ grow tent is another option. They're much more industrial vs. aesthetically pleasing imho as they don't show case the plants. For the price they will give you the most grow space per buck - other than DIY of course. They're geared for production, not for showcasing pretty plants.
If I were doing what you're doing - propagating 1 specific plant en masse, I'd consider buying a stainless steel wire rack and wrapping it in some type of greenhouse plastic. The one I have will fit 3 10x20s per shelf, with some slight overlap both in the front and back. Some of the larger models might actually fit 4 per shelf with no overlap, allowing you to use plexiglass to make a permanent shell.
Dedicating an entire room to propogation is another option. A humidifier can easily keep a room at 70% - adequate for most plants.
Edit- A clear plastic tote flipped upside down would be a decent option as well for small scale propping.