What are some good sensors and where can I get them?

I recently finished building a complete two lane drag race system including: a full christmas tree (with pre-stage, stage, starting, and red lights); stage sensors; red light sensors; and finish sensors. It is all tied to two stopwatches for e.t. and a separate timer that gives reaction time for the quickest person out of the hole.

I finally got all the bugs worked out of the system today and everything works as it should ... that is until the sun comes back out from behind the clouds! The full new price of the sensors I got is $70 a piece from RadioShack and they are meant to be used for a security system. Therefore, I expected them to be high quality and fool-proof. They are not. These sensors are very finicky to sunlight changes even though they are advertised not to be. Once their sensitivity is adjusted, they work great for a while. But as soon as there is a change in sunlight or shadowing, they either go off for no reason or refuse to go off at all. I believe that alot of this can be remedied by building large boxes around all the sensors and reflectors (leaving small windows where needed) but that is alot of additional work (there are 6 sensors and 6 reflectors!) and should not be necessary with a quality sensor. It is beyond me how these overpriced pieces of junk could be considered a security/safety device.

If anyone out there has built a similar system and has either found a better sensor or a way to overcome the problem I am experiencing, I would like to here from you. I have heard of Banner photo eyes (but can't find any) as well as Honeywell (supposedly sold by Newark but I can't find those either). The Banner and Honeywell are only 1/2 to 2/3 the price of mine and are suppose to work good.

I really like the way my system is set up now but, if I can't make the sensors more reliable, it won't be much good to me. Having to readjust the sensors every 5 runs just isn't acceptable.