Ye Olde Inn

I got these Space Crusade commander consoles.
They are made of very thin, brittle plastic.
Does anyone have any suggestions on how to make them more sturdy?
The back (left) doesn't necessarily have to look good.

Looks like you could use anything from plaster, resin, or milliput to put something in the back to stabilize it.
I'd go for cheapest probably. And glue a flat bottom to it.
You could also achieve amazing things with a lighter there. Just kidding. No, am not. Well, duh, kidding.

I'm not sure if it shows, but they are approximately 20 cm long.
I'm not sure I'd want such a big solid chunk of plaster. I'm also afraid if dropping it would actually increase chances of breaking...

But gluing a flat bottom to it is not a bad idea as they tend to mostly crack from the edges. I kinda think it would help a lot.
Still interested in suggestions to harden the actual plastic though.

I can tell you, while Space Crusade is pretty much as easy to get a copy of as HeroQuest, getting the consoles intact is as easy as getting candlesticks intact!
I really want to do everything possible to preserve these!

If you have some enamel spraypaint, (the terminology of "enamel" may vary by region) it might be an interesting experiment to test it out on some other type of flimsy plastic to see the results.

According to the description of these kinds of protective-coating paints, they create a hardened coat around the object, depending on the number of coats, I assume: http://en.wikipedia.org/wiki/Enamel_paint

Interesting problem. Technically (if I remember my materials) you want the plastic to be "softer" not harder (more ductile / elastic), so it flexes rather than cracking.

(1) You may want to spray some kind of rubberizing agent to the inside and seal it to that base you are talking about with a rubber cement type bond.

(2) Unlike the HQ candles, this part looks relatively simple to reconstruct in a very low resolution 3D printer (big smooth features). Then you just smooth over the ridges and imperfections with green stuff / milliput. There must be a fan out there who is willing (if has not already) created a great looking 3D model for printing replacements.

(3) Alternatively, the plastic appears to be "stamped" with absolutely no internal support structure. This means that if you fill the back-side with plaster(?), you can remove the cast and repeat. This could ruin the original piece (chemically or under the weight) and not give you anything usable. You can avoid the weight issue by burying the piece in a container of sand. In fact a tightly packed sand impression alone might be enough to give you a decent plaster cast. Please also do a Yeti foot print.

(4) Similar to (3), fill the part by hand with air-dry modeling clay and remove. For such a big part, there will be cracks as it dries. Just fill them. This could work very well.

I would try a thick layer of glue on the underside. Maybe a few. I don't know what you have available, but I would use modpodge. If you don't have that, it's basically elmers, or "school" glue.
You can brush it on and it dries flexible (to inhibit cracking), usually clear. Let it pool in the recesses to prevent dents on what are the raised areas when it is upright. If it doesn't stick (it should), score it first with steel wool or something.
And/or some of that spray foam builders use. What is that?

The product you want is called "mninimum expanding foam". Spray it into the back.

If you have a ht wire cutter and a steady hand, you can over-fill and cut it back down.

Once done, mount the think on a nice sheet of greyborad, or even better, hardwood.