There has been at least a couple threads about new felt wicks in the Singer 66's and 99's. I've got 5 66s, two 99s and a Sewmore 404 that needs new wicks. I've been looking for a source of thick 100% wool to use for doing this. The TFSR instructions says to use 5 mm thick felt and how to cut them. I didn't want to waste my time chopping up the spool felts sold by lot's of places so I looked and found this place:
They are selling 100% wool felt sheets at 4 to 5 m/m thick for around $3.50.
I haven't bought any yet, but will as soon as I can.
Just thought this might help.