I know that FontLab allows one to change the UPM to something other than 1000. So you could use FontLab to make such a Type 1 font. Not sure if the FDK will parse such a font, though.
Or, you could use t1disasm on a Type 1 font, change the FontMatrix to
[ 5e-4 0 0 5e-4 00 ]
which is effect 2000 UPM, and then double all of the numbers in the decrypted disassembled subroutines and charstrings. Then reassemble the font. Maybe I should talk to Eddie Kohler about adding such an option to the t1utils suite of tools.
There is also Y&Y's FMP which does some handy tricks with Type 1 fonts, but I am not sure if it handles UPM adjustments.