Heli-Coil kits are great, but do require a specific drill and tap to machine the new threads for the insert, so they can be more expensive per insert than some of the other options that use standard tooling. That said, there's almost nothing lower-profile than a Heli-Coil, so for tight spaces without a lot of material around the threads, these are sometimes the only solution.
That said, I just repaired an aluminum fixture plate for my milling machine and used some over-the-counter E-Z Lok inserts, as they used a standard drill/tap for the OD thread on the insert itself, which saved me both time and money in fixing it. They offer both steel (12L14) and stainless steel (304) versions in most sizes, and I'm pretty sure I got mine off Amazon the next day.
Another option with a more positive, keyed locking solution would be a Keensert/Recoil type thread insert, where these can work well in higher vibration applications, lower strength base materials, etc.
