What is a Temporary SAFE Fuse Substitution?

I just recently had to change out a blown TAD EL34 in my BE100. Blew the 1A slow blow HT fuse as well. I can't find any 1 amp slow blow fuses out of the dozens of other slow and fast-blow fuses I have. I wanted to make a post to let others know what can be safe to use just temporarily, even though it's a fact your ALWAYS supposed to use the same exact value fuse as a replacement.

Here's the fuses I have right now that are close:
2A Slow Blow 250v
1 1/2A AGC Fast Blow 250v
500mA Slow Blow 250v

It's it safe to temporarily use a 500mA slow blow in place of a 1A slow for the time being?

Decided to email Dave and he said 1.5 fast blow, so there ya go.