Cal Audio Alpha/Delta Question

Hello guys, I have a Cal Audio Alpha/Delta combo that I have had for about 14 years but never used ti till now, original owner bought it new in 1997. Opened it up and it still has the Cal Audio branded tubes so I re-seated them as the original owner told me that the unit didn't have much time on it because he just hated the way it sounded. I checked the fuse on the Alpha and it blown but I cant find a .3A 250V fuse, and not sure if its fast or slow blow. So my question is can I replace the with a .5A/250V slow blow fuse from a boutique fuse and not have a problem. The original fuse seems to have piece of TEFL in it with a thin wire coiled around it, the only other making on the fuse is 313. Thanks in advance guys for your time and effort.