It's a pity you weren't looking for an engine a few weeks back as I just threw a trailer load of good trimmers and blower vacs out, there were lots of Ryobi trimmers and blowers , I threw out a lot even if the motor looked brand new with virtually no carbon on the top of the piston.
I haven't swapped a trimmer motor into a blower but would think only a trimmer engine with a clutch drive would fit as it has the longer shaft.
I saw a Ryobi blower vac at the side of the road about 4 days ago and didn't bother picking it up.
I would never pay $15 for a trimmer or blower ,I usually fix them and give them away for free ,have sold a lot for $5 each that just needed a spark plug but most of the time I can't even get $5. for one on Gumtree ,I only sell them at $5 if someone asks me for a lot that they can fix.
Most of the time here when I've sold a mower I've said to the buyer you can have a free working trimmer or blower vac ,a lot of the time they say no they already have one and don't want it, so then I say well you could probably sell it for $30 and about half the people then take it.
I don't bother fixing any power tools where if the starter cord breaks you have to pull the whole machine down to get to the cord , just use the engines that have a starter that bolts on the end.
I can keep an eye out for what you are after and send the motor in an Aus post small Prepaid Satchel it would only cost you $10. all up but if it was me I'd look for a better blower vac for free or $5 at a market, swap meet ,auction, scrap metal yard , one guy told me he asks at mower shops for free old equipment that they no longer want and says he likes to repair the old equipment and they just give him stuff for free.
Lately I've been throwing out a lot of newer snippers like the one below but that won't fit the blower vac.
