I took some comparison pics today (borrowed some IG from a friend) and have put them on photobucket.
hereThese are all metal figures so converting the rifles to lasguns is likely to be time consuming. I imagine if you're prepared to put in the effort, there are loads of possibilities...
Most 20th Century periods have miniature ranges available in 28mm these days; WW1, WW2, Vietnam, USSR in Afghanistan, even up to date War on Terror ranges are coming out.
Edit: Just a thought, if you want to avoid a load of conversion work, you could always use plastic Cadians and just replace the heads.
Gripping Beast do some head sprues as do
West Wind though you may have to research the scale differences involved.