Here's some OPL to create a pound sign and put it in a UDG, with character code set by U% (numbered 0 to 7).
The UDG can then be printed using PRINT CHR$(U%), or used in the word processor Autoscribe (by pressing MODE twice and selecting Char to enter the character code, however I think some codes are already used by Autoscribe, maybe 3 worked for me?)
POUND:(U%)
POKEB $180,(U% AND 7)*8+64
POKEB $181,6
POKEB $181,9
POKEB $181,8
POKEB $181,28
POKEB $181,8
POKEB $181,30
POKEB $181,25
POKEB $181,0