I would recomand either glass or a polycarbonate material, I find acrylic to be way to crispy and faster degradeing then polycarbonate.

If you want somthing that never breaks use laminated polycarbonate, thats the same used for bullet proff windows ect. Just get a thin sheet, like 4 - 6 mm. or something.

Personaly I would use a 6 mm hardened glass, as it's alot harder and don't get scratched as easy as any of the two other materials. Here polycarbonate would be alot more ekspencive too, but it's a super material!

Greetings

Build one out of expanding foam, them cover it with silicone and your choice of either coco fiber, gravel and so on, its permanate, and when your wife cleans the set up all she has to do is clean arouind it =) the directions on how to do this can be found on blackjungle.com, just adapt it to build a pool from the same process, Ive done it in the past and it has worked out great =)

hello
They make kits fo this purpose for several sizes of aquariums. I always found it almost impossible to keep a "pond " full of water. No matter how carefully planned the water seems to miss it lol. The best bet is to use a false bottom and raise the substrate above this then you can set a bowl or whatever in it. Direct the stream toward it and the water will be constantly changing. Won't matter if it goes over the side.
gary