Sure. I've owned Minco (MISVF) shares in my TD Ameritrade account. I don't happen to own any at the moment, but no problem buying it.
And in fact TD Ameritrade is a good broker for owning pink sheet versions of Canadian companies.
Five years ago or so I had a Schwab and Fidelity acct. Those did not trade pink sheet versions of Canadian stocks as well as TD Ameritrade does. Since I had a lot of my account in such stocks in the late 00's, I closed my Fidelity and Schwab and went completely with TD Ameritrade.
I have always figured, although I don't know for sure, that TD Ameritrade simply trades the Canadian stock and shows it in your account as the pink sheet version, with the price translated from CAD's to USD's.