DMJJ67,
If you want to replace the playfield with an original blue one (circa 1976-78 only) your best chance for locating one would be on EBAY or Craig's list. Unfortunately, you are much more likely to find a complete table than just a playfield only. The upside is that if you do find a reasonably priced table with a good playfield you could get a bunch of spare parts for later along with the blue playfield. Who knows, you may find a blue TS table in better condition than yours and end up using what you have now for parts.
Thinking out loud, hope it helps............................Tyler.