Accessory feet for Manfrotto 3221 tripod

The round rubber feet of this tripod are okay, but I wonder if anyone has customized his or hers with either better non-slip feet for indoors or some kind of spike or other metal foot for outdoors. The existing feet have a diameter just enough over 1" that typical 1" inner diameter rubber feet don't fit over them; they're not meant to be removed, as far as I can tell. As for spikes, I looked online for camping equipment or walking stick tips but saw nothing I'd try to adapt for under about $40 per piece, way outside my try-one limit. I wonder if there's something that could be adapted with hose clamps.

Any ideas?

Crutch tips should do. Hardware stores usually have several sizes.

Look at B&H Photo. They have all types of Manfrotto/Bogen spiked feet which screw down to rubber pads. If I'm not mistaken, the lower leg diameter of the 3221's is the same as the 055. Call them. The ones I bought for my 055 Pro (CF) were around $40 for a set of three.