Eric, I think you're looking for something similar to the following products. The following sites show boxes that hooks up two radios to the same set of keys, microphones and speakers. There are more examples around the internet as well.http://www.k1xm.org/SO2R/https://sites.google.com/site/rtavan/yccc-so2r-box-product-reviewhttp://www.microham.com/contents/en-us/d161_U2R.html
Here's a DIY setup that also might fit your needs.http://www.dl1iao.com/tech/so2r_basic.htm
The DL1IAO schematic gives some good information on running the same set of peripherals with more than one radio. The control box is something you probably could adapt to your needs in a weekend's work.
Good Luck and 73, Jim W.