You can buy one on eBay for under $100. I have two old and similar Sitex GPS's you could have for the cost of shipping
. Brand new back when they were first made they were quite expensive. They may work
but a new cheap
12 channel handheld GPS
of any brand will perform better.
Myself I like the older garmin
128 external antenna
or the 126 internal antenna. I pick these up on eBay as they are removed from boats that want a fancy color plotter. They can be had quite cheap
and I've bought two. The external antennas can be had for $40 and the antennas can go bad as well. Some of the old technology works well enough but I think that the Northstar and Sitex units are too old.
For a laptop I like to use electronic charts and a laptop and a GPS link. I plot my course and load the GPS with a route
or two then shut down the laptop. I'll use paper charts with the loaded route
and sometimes turn on the laptop if I need to make some changes or make more adjustments than I had planned. It uses the least power and you really want to plan the trip before you leave not as you go.
Piloting a boat while watching a chart plotter can get you into trouble. Many people get to thinking they can watch the plotter and not look where they are going. Much as deer frozen in the headlights. It's a good way to hit a day mark or sea buoy.
You still need to plot courses and positions with day sails
too. Just because you know you are coming back to the same place does not eliminate the need to always know where you are and plan where you are going. The skills you develop now pay off later on.
I also have a small handheld RayChart 400 plotter with a Navonics chip. The screen is quite small and difficult to read at the helm
but it has come in handy. It came with the last boat but I would not go out and buy one. The batteries
are only good for a few hours so you need a 12 volt cable. If you get laptop software
that can work
charts you'll find they are just as nice as a Navonics chip and the ENC
maps are free and a laptop screen is far larger than any chart plotter made.