I reckon a good old non clutched dyson belt will fit 95% of those, they always do!
Otherwise pattern will be fine!
I rarely use genuine belts unless I happen upon them/its a collection/museum machine, although kirby's hate them! They slip and slide all over the place, never seen anything like it!
Your also lucky those machines dont use a silly toothed belt! Vax are good for toothed belts, mainly because they used about 3 variants for probably 5 years worth of shit. Miele? Try getting a toothed belt for a powerhead.... Sebo belts used to be well tricky and expensive to come by, probably because they dont usually break as the computer stops it getting that far
I've got some vitesse belts! Would cost me more to just post them than youll get a set from ebay posted for! Plus they'll come in handy one day. If you fiddle about with tat like that, buy a cheap job lot of random belts. Then, you can take 5 minutes, tip the box out and offer them up until one is the perfect fit! Then tidy up the box...