Most of the tickers are traded on Canadian exchanges (NEO, TSX.V, CSE). If you’re in the US, I believe Interactive Brokers (and others) will let you buy stocks at these exchanges. You can do all this self-directed, no need to involve a processional.

If your current broker doesn’t allow Canadian venture/OTC stocks, $CMPS is the only ticker traded on NASDAQ so far. $MMED is expected to uplist to NASDAQ in the near future.