A pair of 5mm-compatible accessories based on the two large guns that were included with G1 Vortex, sized more appropriately for
Transformers: Combiner Wars Vortex.
On the opposite sides from the 5mm pegs are small 3mm pegs, which can be used to attach the guns to the holes in Vortex's elbows, although this is a very weak connection and likely to stop working properly after a while.
A version of Vortex's handheld gun is available
here.