I have a few older T4 rechargeable flashlights. It works well but has a 200 lumen bulb. I see the newer models are significantly brighter. I'm wondering if anything besides the led has really changed. I'd like to try putting a newer LED in it but don't know if it is possible or where I could get one. If anyone has done this or knows the part number I'd be happy to try.
hello boe_d and welcome to CPF.
Inova made/makes some wonderful lights that are tough as nails. One of the prices to pay for that ruggedness is that the light is pretty well sealed up tight. The "bulb" or LED emitter is not made to be user serviceable but hobbists do occassional "mod" these lights or perform "emitter swaps". The Inova lights are notoriously complicated to open and generally I'd recommend treating yourself to a new light if the previously one has served you well.
If on the other hand you'd like to dive into taking one of these apart to see what it's all about (or there's some sentimental reason you want to keep these particular lights), you can search on "Inova" & "Freeze open" and you should be able to get some history on the matter.
Then do some searches on "LED reflow" to read up on how to perform a change of the LED emitter.
That doesn't quick get you there yet. There's still a matter of mating the emitter type and MCPCB (Metal Core Printed Circuit Board for mounting the LED) to the reflector for focus.
Lastly there are some capable members that offer their services for hire that might be able to help with a mod/swap but the Inova's are a challenge.
Good luck.