I think 3068bpv** (*=0-9, a-z) will be suitable, similar as the numbering for collectible minifigures.
This allows us to use 36 x 36 = 1296 part numbers, and we should allocate the next block when it runs out.
This allows us to use 36 x 36 = 1296 part numbers, and we should allocate the next block when it runs out.