Torches are a different ball park as batteries are internal. The Chinese are offering quite a few which are dive rated.
I have have done a few conversions to Kowalski dive lamps some of which were bought by the customer cheaply off eBay as not working.
I solder up a copper insert with good contact to the aluminium case for heat transfer, an array of about 6 18650 Li Ion cells, and 4 Cree XM-L LEDs to give a maximum output of about 4,000 lumens. This buried the original bulb.
Looking at Kowalski lamps now, the basic design appears unchanged.
I was charging about ?100 for the conversion. But before anyone gets a hard on, there are some components that I cannot obtain anymore. When they become available again, if, I will offer the conversion on the website.