I buy them in my trading terminal on open market. They trade under 'pinkies' simply because it would cost a lot of unnecessary cash to list them on Nasdaq. As you know there are only 3M warrants out there.
My broker (IB) didn't have them last week, I talked to them and sure enough
I didn't have any free cash to buy so I had to sell some common shares first. I, however, wasn't sure if they would be possible to buy, so I sold common shares in increments of 100 and would buy warrants in increments of 200.
If you believe SLTD will hit 8 and above, it makes sense to buy warrants, you essentially will be able to double your position.
You can consequently either sell them on open market or submit a ticket with your broker to convert them through company (essentially, SLTD will issue new shares at 4.15 for you)
Warrants are good for another 59 months from now. I personally think it's well worth it.