Who makes....
 

the scooters that Northern Tool and Equipment sells (sold)? My neighbor has one that was ridden maybe three times up and down the road, and then parked for the last three years. I'm just wondering if I'll be able to get parts for it before I go over and make them an offer.

I think they have an "HY" prefix to their model numbers.
I believe this corresponds to Wuxi Hongyan Motorcycle Co.,LTD
And no, I've never heard of them either.

Another maker that uses that prefix is HUAWIN, their site is at:
http://www.huawinmotor.com.cn/hot-product.asp
This make appears in Craiglist a few times so it's possible that they're still being imported to the US.

if it a honda clone or yamaha clone 49 50 125 150 250 260 300 cc

we sell parts for them them as many other do to.