Got the most recent Highland Woodworking catalog, and spotted a new product: replacement blades for Multimaster and clones that don't cost an arm and a leg.
They say:
If you love your Fein Multimaster tool, but squirm at the cost of Fein's blade accessories, Imperial blades are made just for you. Proudly made in USA, these blades fit the Fein Multimaster, Dremel Multi-Max, Bosch Multi-X, Chicago Multi-Tool & Craftsman Multi-Tool.
So they'll fit my Harbor Freight $34 vibrator. The blades have an odd hole pattern, probably to fit all these different tools.
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(I've ordered stuff from them, so can vouch that they're legit and give good service.)