lzss0 is just the normal LZSS with the only difference that initialize the window buffer with a NUL byte instead of a space.
Any implementation is ok as long as it has the default settings: EI = 12, EJ = 4, P = 2.
The one in quickbms is big because it covers all the settings, probably you want something much simpler and easy.
For example this one is from Okumura (who wrote one of the oldest public domain implementations, the following seems a short uncommented rewrite):https://oku.edu.mie-u.ac.jp/~okumura/compression/lzss.c
As you can see EI and P are different so you must set as I said before.
And obviously you must change the two occurrencies of the "space" ' ' to 0.