Small needle nose pliers or circlip pliers are what you want for the retaining rings with the two small holes in them. Any hardware store will have them, or go crazy searching ebay.
LED's - there are so many to choose from, depending on what the intended usage is. Here's a good reference chart.
The XM-L2, XP-L, & Nichia 219c variants are common for use in basic single-cell lights, such as a Convoy S2, or C8.
Non-counterfeit LED's can be sourced from places like this, or this for discount prices. There are many other options.
The Driver must be matched correctly to the LED & Cell/s. Here is a selection of common drivers.
The AtTiny 13/25/85 series of MCU's on the popular drivers that are in use enjoy a wide variety of custom firmware made by some very talented people here. Here's a good guide if you ever want to 'flash' your own driver.
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