You do know that is only relevant if you intend to save the seeds and grow them out the following year? Cross pollination does not affect the fruit produced this year only the seeds in that fruit.
But if you do want to save the seeds and maintain a pure line, best is to bag the flowers before they open and get pollinated. Next best is to plant them a quarter mile apart. Third best is to plant at least 25 feet apart with some barrier crop in between.
When I post links, I'm not usually trying to be like -- "you should know this was described before"... More like "oh I remember seeing that somewhere ... Here it is! Take a look and see if this helps "
Organza (sp) bags work well. I got mine at a local craft store (Micahael's). I have strayed away from it though in my hot humid climate I lost more trusses with bags than not. Maybe I should have don't this earlier in the season.
If you can't find anything PM and I can send you a few.
Yes as Tom said save seed from first fruit bagged or un bagged. That lessens the chance of a insect/wind blown cross.
I myself enjoy the bee crosses as many do. Save a lot of seed from several fruit/plants even if some are crossed chances are very high that not all of them are. Even within the same fruit, every seed in a tomato was pollinated separately. So it is possible to have true seeds and crossed seeds in the same fruit.
You may have to ask where they are but you should find them in the wedding section. If it's anything like my Michael's every time I go there everything has been moved around. Get the biggest size, they are easy to use since they have a drawstring. Just put over blooms and cinch the top, simple.
Just go for the simple white they are the second from the bottom on this link.