For reference in tokenizer version 0.9.2 there is a function to load spm model. You need to run these two commands before to install the dependencies

pip install protobuf
wget https://raw.githubusercontent.com/google/sentencepiece/master/python/sentencepiece_model_pb2.py 65

then you can instantiate huggingface tokenizer using pretrain sentencepiece model as
tok = tokenizers.SentencePieceUnigramTokenizer.from_spm("spm.model")