I use the Aquatec integrated Octo with the built in SubDuck/Dive Alert. They also make a power inflator with it built in. I suggest these 2 models to my students and club members over the others. As for not being able to get service parts I have contacted Aquatec and can get service parts for the Octo. As for the power inflator many manufacturers suggest use until failure and then replacement. Standard replacement parts will work for the power inflator at any rate.
The other reason for my suggestion and opinion is that last year there was a recall on many of the add on alerts for failures associated with the couplers. The use of these separates actually adds an extra failure point to your gear and of course as Murphy’s Law would have it that law reared its ugly head. By using either of the Aquatec models that build in the noise maker that extra failure point isn’t there.