where do they sell F5al12.5v fuses?

Answer 1

that isn't quite enough info and probably not entirely correct.
there are no 12.5v fuses - 125v yes.
go here and do your search

http://www.mouser.com/search/Refine.aspx?Msb=0&Mkw=fuses&Ntk=Mouser_Wildcards&Ne=254145+1447464&Ntx=mode+matchall&Ns=P_SField&Ntt=*fuses*&N=1323038%20254145

You can try digikey.com also

it is probably a 5amp 125v fuse. but you need a little more info to nail it down and read the number from it more carefully.

both may require a min order value or charge a fee for less of an order.

Answer 2

You could get it at all electronic shop where they sell Electronic components