The third Minsk had a ripped seat cover. A cheap fix, was to order a metre of the vinyl fabric used for motorcycle seats off fleabay, for around £10, including postage. The old cover consisted of three parts stitched together, a front, top, and back piece. So I took it and the fabric to a local seamstress who does clothing alterations. She used the old one as a pattern, and made me a new one. Charge, only £4. Fitting was easy enough, as its a metal seat base with the metal tabs bent out. Stretch over, piercing the fabric, replace the wire reinforcer which goes round the base, then press the tabs back over :
All modern seat bases are plastic obviously, but you can staple straight onto the plastic base with a staple gun easily enough.