If you don’t have a blow lamp and you wish to use an alternative, the best options are the following:
A gas torch is very similar to a blow lamp, as it can also be used for soldering copper joints. However, it is an industrial version. It can reach much higher temperatures and burn for longer due to the bigger gas cylinder it uses.
A heat gun is a corded, hand-held tool which can produce a medium heat over a wide area. However, it can only be used for stripping paint and moulding plastic as it does not produce enough heat for soldering.