What blank media are you using? If anything other than Ty 8x you may be able to add years more use by switching. If your already using Tys then you may be out of luck. No to replacement burners, DVDRs use proprietary burners. Some hardcore Pio users like Citibear have taken specific drives(out of non HDD Pios I believe) and transplanted them in HDD Pios(retaining some of the original parts to make it work) but it sounds not for the faint of heart.
Pios are no longer made and any HDD Pios are as rare as hens teeth
You could try and track down a Canadian Sony(Pio clone) but they aren't that easy to find either.
The Magnavoxes have a large following but personally if you are use to your Pioneer I'm not so sure you would be happy with a Magnavox. You may
be happy with a international
Panasonic(~$400 for a new grey market tunerless Panasonic) but be forewarned the MN system is quite different on a Panny than Pio and I would think it would be easier to go from a Panny to Pio than the other way around. The Pannys make very nice recordings and have a comparable editing system to the Pios but they will be different.
You could try a Magnavox from W/M and if not satisfied they have a excellent return policy, the grey market dealers of the Panasonic tend to charge a restocking
fee, if they even accept returns. I'm very happy with my grey market EH-59 but then again I'm a Panny guy and have used them for years
Citibear has many Pios and a couple Maggys, hopefully he'll add to the discussion. I think Wajo has a 640 and for sure several Maggys which he really likes. If you haven't already, check his sticky thread at the top of your page for lots of great information on them.