Can you sew at all? My wife made seat covers for years out of lycra fabric. Very simple pattern, just trace the outline of the seat, then sew about a 3 inch strip to the seat top cutout. Hem the bottom of the strip, then put in a shoelace. The lace will have its knot to stretch it tight at the rear of the seat.
If you can't sew, then just take a lycra square and staple it to the seat on the underside, stretching it tight. Start with one staple at the nose, and one at the back. Then start working on the main wide section of the sides. This will result in a few folds of lycra at the nose, but if you stretch it tight and carefully, you can avoid a fold big enough to chafe.
This worked really good for us for years, in our climate, black seats are just stupid, so we'd make our seats any color but black. I really liked white, or at least lighter colors of lycra.