You'll get very blue light from most cheap LED torches. Get one with a good quality LED in it though and the light will be close to daylight. CREE are the probably the leaders in high output high quality LED elements with the CREE XM-L2 being the current popular element. It kicks out about 1100 lumens in its brightness form. Popular brands known to produce good quality flashlights (torches) using CREE elements include EagleTac (or sometimes EagTac), Klarus, Fenix and Nitecore. I have a Klarus light that makes very nice light at about 980 lumens. It doesn't "zoom" though which makes it less useful for regular lightpainting (I stuff it into a T8 tube Eric Pare style). Almost all of the recent good LED flashlights run on one or more 18650 cells. These are around 3.7Volts and are used in most Lithium Ion batteries, and loose inside vapour inhalers.
Here's the list I made when last looking for lights for the tubes - although I was mainly looking for very narrow lights on this occasion to get 2 in a T8 tube so the bigger ones are not on this list:-
https://docs.google.com/spreadsheets/d/1AwN7blJ-r3NT98mp8kSd-sheWSvsm01yH2DNcOhPXf4/edit?usp=sharing
Just search Ebay for "XM-L2 <brand name>" where the brand name is one of the 4 above and read the specs carefully

. Note: EagTac is hard to get in the UK.