EDIT: wrong gens, doh!

Looks like an older gottlieb. I'd try to track down a replacement, they play a lot different.

I'm not aware of any place you can buy the full assembly, but here's a diagram with all the parts: http://www.planetarypinball.com/reference/partsmanuals/BLY_Parts_1979/files/mobile/index.html#66

Many were included with your kit. The base plate is usually eh hardest part to find but it appears marco has them: http://www.marcospecialties.com/pinball-parts/A-613-41

Hopefully you can piece one together, or I'm sure someone has a spare playfield sitting around and can sell you an original at worst

Wow, never seen that style on a bally before. Looks like I had it backwards! I doubt you're going to find the older style for sale new though... Since you've already got the kit it might be worth tracking down, or upgrade to teh newer style...