backlight that attaches to backrack?

^^^Yup, that is the bracket I use to affix my Planet Bike blinkie to my Topeak bike rack. Works great!

I use the rack mount that cyclingfool mentioned. I clip my PB Turbo flash into it. You may want to get a full-bolt-on light if you don’t want to mess with unclipping the light from the rack. Peterwhitecycles and RivBike both have the “B&M Topline” steady light that bolts to your rack, but it doesn’t blink. I have the dynamo version of the TopLine light and it’s very bright. Note the spacing on the rack tailight bolts will be either 50mm or 80mm. Measure yours to see which lights will fit.

Rack mounted lights on Peter White: http://www.peterwhitecycles.com/taillights-bat.asp#rackmounted

Rivbike Topline battery light: http://www.rivbike.com/product-p/lt009.htm

@cyclingfool 81777 wrote:

Depending on which brand light you have for the back, you should be able to pick up a rack mount like this one:

http://www.amazon.com/Planet-Bike-Tail-Light-Bracket/dp/B000IQEAK2/

It’s probably unlikely to be an Amazon Prime item, but I’m guessing it’s something a bike shop might have on hand.

I ordered the bracket that you listed from Amazon few days ago after not finding it in many of the local shops, then yesterday I went to Bikes@Vienna, and saw that they have it for $4.99, and they have 2 left. 😡

I am jealous that you have a rack that has a place to mount a light! I had to drill holes through a steel rack for that purpose.