hey guys, im in need of some info regarding a chartplotter,

i am in the process of doing up a 3.8m dinghy, i already have a lowrance elite 3 inch sounder but without the chart plotter. i am wanting another unit which i can just use as a chartplotter, i am wanting maps and not just a gps. 

something around the 3-5 inch size and relatively cheap.

any info regarding products that i should look at or if anyone has a unit they want to sell would be appreciated 

Thanks,

Nathan