Red plant

Alternanthera reineckii ''roseafolia' and Ludwigia glandulosa would do well in your set up.

is there a good online store where i can find these? they seem rare

Try AquaBotanic.com. I've ordered plants from Robert in the past and was completely satisfied.

AB would be a good place to look. You might also want to try the for sale section of APC.

are these plants easy to care for? any other suggestions?

About the easiest red plants you will find. They aren't too rare. I have seen A. reineckii for sale in local pet shops quite often. Just make a new thread on the for sale and trade section of APC

http://www.aquaticplantcentral.com/forumapc/sale-trade/

There are other reds but you will need high light and pressurized CO2 coupled with good ferts in order to get them healthy and red.

You might also try Ludwigia repens. Also fairly undemanding. Tops of the leaves might not always get real red, but the undersides are.