As Hopkirk points out, hardly any torches use filament bulbs these days. I can't recall seeing any on sale for over a quarter of a century.
If you can find a local, independent hardware store somewhere, they're quite likely to sell torch bulbs. (I feel sure that the one that we had until recently would have had them. They even sold things like individual cable ties! Sadly though, they closed down last year. There are still several little hardware stores around Ipswich though, where one might hope to find obscure things like torch bulbs. So perhaps there's somewhere similar in your own area?).