You really should have enough spare tubes to get you through a gig anyway. This means at least a full set of power tubes, one spare preamp tube of each type the amp takes (although you can usually get away with substituting a 12AX7 for any of the 12A*7 types), and one rectifier tube if the amp doesn't have a solid-state rectifier option. And at least two spare fuses - if a power or rectifier tube goes, it will usually take the fuse with it and it's no good having spare tubes if you can't power the amp up again! (But, if you've changed both the power and rectifier tubes and it still blows the fuse, there is something else wrong and more fuses won't help... so two is enough.) *Under no circumstances EVER use car fuses, foil, guitar strings or other 'emergency' replacements for the proper fuse value* - you'll just seriously damage the amp if anything else is/goes wrong.
You can use a solid-state rectifier plug-in as a get-you-home in most tube rectifier amps, but with vintage amps you should make sure it's the type with a simulated voltage drop as well, or you risk blowing filter caps or other parts. You could also use a higher-rated rectifier tube if you have a spare one (eg GZ34 instead of 5Y3), but you also need to be careful about the change in voltage.
