Madeira is great for decorative wraps.
It does require colour preserver as it is meant for sewing/embroidery and has a silicone coating which can cause fisheyes in the epoxy sometimes.
One trick I have been told is to drop a tiny offcut into the epoxy as you're mixing it.
I always use CP, so I can't say if this works 100% of the time to stop fisheyes.
Madeira comes in #40 which is slightly smaller than size A thread.
I use it for underbinds, but unless it's a light stick or fly rod I wouldn't use it for guides.
The best prices will be found at online shops that supply embroidery thread.
When we last bought it (years ago now), we paid about $2:00 per 1,100 yard spool. Mind you, we bought about 150 spools.