You do need to know what the actual fuse is, not a generic description like you listed.
Size (length) is going to be critical to actually fit the fuseholder ...
Should I gather you have the original fuse in hand??
If its a Buss brand fuse, (or something like that)
it should have a part number stamped on one of the silvery bands ...
3AG or something similar ...
Try an actual electronics outfitter like Capital Electronics in Gaithersburg, MD -
instead of the auction site ...
You should be able to get a box of Slow Blow fuses for $5 or so ...
https://www.capitaltristate.com/
or maybe someone like
https://www.suburban-electronics.com/
http://www.jblproservice.com/pdf/Vin.../JBL-SG520.pdf
On page 22, it says - 4Amp 120 volts slo blo
on page 28, it says 3/10 Amp slo blo (3 to 10 amps?)