I’m trying to do the exact same thing. I mentioned that I was planning on buying an aquarium airlock. There are two big problems with the whole idea, and I’m not sure how to get around them.
Problem number one is maintaining even vacuum pressure. The brava had a pump that maintained relatively even vacuum pressure all night. The pump cycled on and off to maintain the pressure within a specific range. I think the range was between 15mmHg and 30mmHg. There are still used Brava pumps for sale, but the listings all say that they no longer cycle on and off, meaning that they can’t do their job and maintain an even pressure any more. They’re basically useless and dangerous, but still much more expensive than a basic hand pump you could buy at a hardware store. I used to pump ages ago, before I took a looong break, and back then I remember people on other pumping forums saying that it was possible to modify an aquarium pump to maintain even pressure. I’m not mechanically inclined, and I don’t remember the details or where to find those posts. I don’t want to use an electric pump at night unless absolutely necessary, and I don’t want to wake up more than once per night to hand pump, so I’ll have to find out the hard way if it’s possible to maintain suction for at least 4 hours with the airlock. Even if the cups manage to maintain suction for that long, the vacuum pressure will reduce over 4 hours. If the hand pump gauge reads at least 15mmHg after 4 hours, I’ll know that the pressure in the domes never dropped below the minimum level. If it does drop below 15mmHg, I’ll have to find out how to buy and modify an aquarium pump to maintain even pressure, or just give up on the idea of 8-10 hr pumping.
Problem number two is padding. The Brava had extremely thick adhesive silicone rings, like those gooey stick on silicone bras. From what I’ve read, it completely prevented nerve pain in the armpit nerve that tends to get pinched while pumping. I’ve heard that Noogleberry’s silicone rings and Bosom beauty’s rings are the best available right now, but they’re still nothing like Brava’s massive adhesive rings. Bravas rings tended to cause skin breakdown after long hours of wear, and I’m not sure if non-adhesive rings would do the same. Brava recommended and sold “skin barrier wipes” which were the same as the kind used for other medical devices that attach to the skin. I don’t know if it’s worth buying skin barrier wipes from Amazon just in case, but I might try it out if I start experiencing major skin irritation. I also bought 3m tegaderm tape for my nips. I remember how much they hated being pulled on when I used to pump.
Most of the stuff that I ordered got stuck in customs or something, and it’s taking forever to get here, so I haven’t tried any of this stuff out yet. If you try this, please let us know how it works out for you. I’m very interested