Decent backless bra (does this exist?!)

[thisfalseinsight]

I bought a lovely dress with an open back and I'm looking for a backless bra to wear under it - all I've seen are those stick-on things, but can these actually work for anyone but impossibly perky 20-year-olds? To be honest I am not especially busty so I don't actually need much support; I just don't want anything showing through (some support would be nice, though). Can anyone recommend a bra that might work for me? Bonus points if it's not too expensive because I only paid £30 for the dress and I don't really want to spend more than that on the bits to wear under it!

What size bra do you take? How low does the dress fall?

You can get converters to turn normal bras into low back bras, like this. I've not tried them though. There used to be bras about in that general sort of style but not so much now.

this looks very good but is maybe more than you'd want to pay.