Aftermarket parking sensors

Does anybody have a reccomendation for an aftermarket parking sensor system? We have a backup camera (w/display in the rear view mirror) but it's a 155" wheelbase GM van and there's just a lot to account for when backing up. You can't just stare into the camera's display or you'll end up hitting something with the front end or sides. I'd like a system with front and rear sensors, or just two separate brain/beepers, one for front and one for rear. Something that will mainly just give audible alert if your attention is elsewhere and you're about to hit something. There are tons of extremely cheap ones (some under $20) on Amazon and eBay that all seem to be the same Chinese product with various not-so-creative brand names made up for them. They have some seemingly legitimate positive and negative reviews but all seem to have their share of fake reviews. I'm hesitant to drill a bunch of holes in the bumpers of a vehicle for these. I saw that Alpine made one briefly but it's been discontinued. They can be found "new old stock" on eBay and what not for $150. I may go this route but it would be based solely on the Alpine name brand as there's not much information out there on this short lived product. I'd prefer a current production/supported item if possible. Then there are the middle tier of systems that are around $50-100 by Echomaster and Crimestopper, which seem to have products that look a little bit better than the commodity eBay/Amazon Brand X ones but still limited info out there on them. There's really no obviously valid choice(s). I don't mind spending more than $20 on the system but I don't want to do so simply to get the same product with a more recognizable name stamped on it. So, does anyone have any recommendations on ones to avoid or pursue?

Rostra makes a nice unit that I use

That one looks decent. Apparently Bosch (who makes the majority of OEM systems) makes an OE style aftermarket kit too but it's hard to find in the US.