If you are looking for a low cost alternative, it is my understanding that the 67-68 B-Body convertible top switch (part no 2820423) will work and it looks identical (at least to my eyes) to the e-body switch.
Part number 2820423 is also the tailgate power window dash switch for 1967 mopar station wagons - so if you can find one of these cars in a salvage yard it might be worth a look.
PG classics is selling a re-production of the e-body switch for $195 (page 162 of the new catalog).