I've got non-runflats on my R99s, and I've swapped the entire under-floor pack to a genuine MINI kit with the compressor and tyre sealant.
I think others in the same situation carry a bottle of something like
Holts Tyre Weld and a small compressor like the following:
Michelin 12v Digital Tyre Inflator Halfords 12V Tyre Inflator
I would have done this as it's much more cost-effective than changing the underfloor pack, I just happened to have a compressor/sealant pack spare at home
