For some years now, I and several other forum members have used the excellent stranded silicone rubber wire which forum member Phil Marrison 'SWB-18' supplies in several vintage colours. Apart from looking far more in keeping than modern gaudy looking PCC insulated wires, it's heatproof and strips really easily. It's joy to use and Phil can supply it in two gauges, the thinner of which I've found to be fine. I've usually stocked up at the NVCF where Phil usually has a stall, but of course Retrotech as the NVCF is now known, is on hold during the pandemic, and I stocked up well at the last NVCF.
Phil visits the forum regularly (he's looked in today).
I'm sure he'd be happy to give an update on prices, colours and availability to anyone interested via a PM:
https://www.vintage-radio.net/forum/member.php?u=2271