Get their e-mail addresses and phone numbers here.
Call the National Republican Senatorial Committee at (202) 675-6000, and call the Republican National Committee at (202) 863-8500 (option 1).
Also, yesterday John Hawkins of Right Wing News had a great entry about where the bill is standing right now:
My source tells me that this has left a sour taste in the mouth of a number of Republican senators who are upset that Mitch McConnell is cooperating with Harry Reid to curtail the rights of Republican senators. Moreover, there's a growing fear that a dangerous precedent is being set here that could be used against Republican senators again and again as long as they're in the minority. After all, if the "clay pigeon" strategy is used against conservatives on the immigration issue, who's to say it won't also be used against them on any number of issues in the future? According to my source, this is causing a lot of nervousness amongst Republican senators and it has Mitch McConnell acting very defensively behind closed doors about working with Harry Reid to roll members of his own caucus. Because of this issue, my source tells me that the vote for the "clay pigeon" strategy is no longer a slam dunk and it is possible that the "grand bargainers" may not be able to get 60 votes to put the bill on the floor as a new bill. If that turns out to be the case, the bill is dead.
Make sure to read it all here.