Custom Divers: unit has has mixed/poor reviews here on SB. (leaky, out-of round shaping, poor customer service all reported) I have no personal experience with this unit, nor do I ever plan to.
HDV SeaTek : (I bought 3 some yrs ago) never even bothered to dive them, just a single O-ring seal, and a klutzy 3-piece clam shell design which I didn't really like. Molded plastic, not Delrin. (still have then in my spares box)
Narked @ 90: (bought 2 some years ago) quality Delrin, 2 O-ring seal, but very small internal capacity, enough for a very small PLB (it appears to be custom cut inside for a specific PLB unit but I don't remember which unit/brand it was designed for.) Went out of production years ago. (In my spares box now.)
McMurdo: Aluminum (bought 4 so far) Highest quality/built like a tank/ but a touch heavy as a consequence. Empty weight per the manual 0.9 kg. Can be a little stiff to open/close but easy to remedy by coating the (3) internal O-rings/threads with christolube/silicone.
Light Monkey: I have no personal experience (yet) with them, but they seem highly rated. I am looking at getting a 'mini can light' set up from them soon, so a custom canister would be an option.
IMHO, the only 2 real/quality choices are: McMurdo and Light Monkey custom canister.
The McMurdo is the only unit who's owner manual lists the specs for the replacement O-rings as well, which bodes well for long term ownership.
The replacement O-rings are available @
www.theoringstore.com
part #'s:
N2.00X082 (2mm X 82 mm Metric Buna-N 70 O-ring)
N3.00X078 (3mm X 78 mm Metric Buna-N 70 O-ring)
---I house the McMurdo canisters inside a pair of Hollis mask pouches, which appear to custom fit the canisters so it looks OEM, not home made. I use some short 'spero coils' from the Trident catalog to attach the canister to the bottom of the pouch drain holes, so I can unzip the pouch, lift the canister out of the water, and open it at the surface, to minimize water/pressure exposure of the electronic items to seawater/pressure (even though the PLB and Cobra Marine radio both float and are water proof rated pretty well anyway). The 'coil' also prevents me from accidentally dropping the canister to the bottom of the sea.
I do quite a bit of custom scuba design/mods on my gear, so I take all the bits/pieces/components out there from all the assorted scuba gear manufacturers and mix/match/repurpose elements to invent/deploy some really cool/exotic 'hot mods' to all my scuba 'toys' that are well beyond anything mass market scuba manufacturers ever dream of ! I also want all my 'mods' to look 'OEM', not jury-rigged/home made, so everything looks professional. Sometimes I feel like 'Q' inventing cool gadgets for James Bond !