Small comfort but there's a modern copy available that is said to have precisely the same sound and it costs only $418,37 (at today's exchange rate):
https://www.thomann.de/gb/roland_tb_03.htm?ref=intl&shp=eyJjb3VudHJ5IjoiZ2IiLCJjdXJyZW5jeSI6IjIiLCJsYW5ndWFnZSI6ImVuIn0=
Any chance of you coming to Germany? Thomann has not only a shop but also a studio and a huge stage where you may try any of their equipment, including that 303-remake and any bass they have in the shop

I could give you a lift from Munich or Nuremberg airport.
This trying out has its side effects, though: last time I was there I only meant to buy an amp and came home with the amp, 2 guitar cases, a few miles of cables and strings, and a Fender Jaguar
If you'd like the real thing and can handle a soldering iron, here are the schematics for the original 303:
http://machines.hyperreal.org/manufacturers/Roland/TB-303/schematics/