The only reference I could find is a 10mm x 38mm fuse size (0.406x1.5"), such as this:
http://www.littelfuse.com/products/fuses/industrial-power-fuses/midget-10x38mm-fuses/flm.aspx
http://www.alliedelec.com/littelfuse-0flm008-t/70184536/
This is a nonstandard fuse size with regards to audio equipment and there is not a vendor who makes an audiophile fuse of this size. The best I could recommend is to buy a bunch of the above "littlefuse" brand (I would recommend a slo-blow for your amp, like the FLM series above). You can use some of them in the amp. I would contact Audio Magic directly and ask them if they would do a treatment on your size fuse (you could send them a bunch of fuses). What Audio Magic does is take a normal 5x20 or 6x32 size fuse and drill into one of the end caps. They fill the fuse with an anti-vibration solution (they have different solutions, even bee's wax). Then they re-solder the hole to seal the fuse. They actually use the "littlefuse" brand for these upgrades. It may cost you more than a standard Audio Magic fuse, but this may be your only option.