Atwood makes a "tubular" one that is generally mounted "inline" in the engine compartment (run dryer-style hose from near the carb out to a transom dorade, but many people still prefer the "squirrel cage" type mounted inside the transom under the coaming, which gets the electrical motor out of the engine compartment entirely. I prefer the latter because I can hear it working via the dorade. You need to run the blower for four minutes by Canadian law, but I fudge this slightly by virtue of hanging the keys on the thru-hull seacock: because I have to open both the seacock, the fuel **** and I give the diaphragm a couple of tugs, I get to have a good look and a good sniff there. If all is clear, I usually fire it up after 90 seconds or so.
I will run the blower on occasion when underway, as motoring or motorsailing with a following wind can put fumes into the cabin. Which is a little too "auto shop" for my taste.
Roger that on the ignition-proofing, regardless, just as you need a non-sparking "marine" alternator for the same reason. A gas sniffer doesn't hurt, either, nor does wiping a dry rag under the fuel bowl occasionally and the annual inspection of the rubber O-rings and clamps.
Gas isn't as dangerous as people make it out to be (you don't see speedboats and cabin cruisers exploding much, do you?), but it wants a fairly strict safety routine and is ultimately less forgiving than diesel.