I can't imagine not having a GPS chart plotter, as fog is often of concern. To me a depth sounder is also extremely important, especially when boating in rivers and lakes.
Ebay can usually produce a viable product new or used for a reasonable price, be it a replacement VHF with built in GPS, or a chart plotter with GPS. Heck a post on this board might produce something like a Garmin 441 for supa cheap. We have a website in the USA called Craigslist that always has a bunch of chart plotters for sale.
A GPS module for some radios is available but at what cost?