Most of the dealers will sell tubes like this on eBay. Look for tubes with matched constructions and good test results. Some money can be saved by getting two tubes that are an internal match but branded differently.
Also, check the sellers feedback and other items to get a feel for who you're buying from.
For most of the online vendors, buying two 45's means you might just get a random pair. For the other dealers, you'll end up paying something like $300 a pair, I see some nice looking pairs on eBay from good sellers for under $100.
On the other end, you could get a new set of TJ's as well.
-PB