I haven't done it and done have any recommendations so you can now quit reading my response if you want...
I was thought about doing this, but we were in a tiny apt with our first and low on $$. Then I had my first. With all the other huge baby gear/stuff, I am so glad I didn't have it to haul around with me. They end up large (of course), so unless you know where you will display it, its big to haul around! IMHO, I'd put the money towards awesome maternity pics (small, easy to frame/hang, easy to move!). But again, I didn't do it, so my opinion is moot!
I did it with #2. We did maternity pics with #1 and wanted something tangible to represent my pregnancy with #2. It was easy and a fun thing for DH and I to do. I don't really have any recommendations. The kit I bought had all of the necessary materials and all sorts of helpful tips. I didn't paint it or even smooth it afterward. I poked a couple of holes to string picture hanging wire and it's hanging in our bedroom. I like it. I do wish I would have taken newborn pics with dd#2 inside of it but didn't think about it at the time.
Re: belly casting
I haven't done it and done have any recommendations so you can now quit reading my response if you want...
I was thought about doing this, but we were in a tiny apt with our first and low on $$. Then I had my first. With all the other huge baby gear/stuff, I am so glad I didn't have it to haul around with me. They end up large (of course), so unless you know where you will display it, its big to haul around! IMHO, I'd put the money towards awesome maternity pics (small, easy to frame/hang, easy to move!). But again, I didn't do it, so my opinion is moot!