In Chas521's IGO 8.3.5.183522 version, the cursor is presented by a Blue Honda, as he wrote "This is MY personal program with a blue Honda Civic cursor".

I didn't like to navigate with his Honda, I want to do it with VW Golf. I hope he wouldn't mind.
Before starting our changes, make NOW a backup of your working program.

First, we need to choose our favorite car. Download the 254 Car models for Primo

Since we have no idea what to look for, unzip the chosen zip file. You will find there 2 BMP files (icon & topview). If it was just about replacing this files, I wouldn't write this tutorial.
We don't have this 2 files in our working folders, But in the unzipped files, there is a file named "Golf5.mdl".
In the Gfx folder, you will find 4 files with this prefix - car, car_ghost, car_gray, car_night , and they are all same file size and same date creation. Sort the folder by date and you will see another file with same date - civic_blue.tex. BINGO!!!
My senses say that this is what we were looking for.

Copy "your_car.mdl" 4 times, 1 for each file name - "car.mdl", "car_ghost.mdl", "car_gray.mdl", "car_night.mdl".
Looking for the .tex file, I see a very big difference between the original "civic_blue.tex" and the "car_grey.tex" that we have, so I'm not sure about its task. I've just copied this file, and named it Golf5.tex.

It's about time to check our work. Turn on your device, You should see your desired car floating on the map. If you don't like the size of the car, edit the "sys.txt" and look for:
[map]
3d_scale_carmodel=1
3dcarsizemul=10000
3dcarsizemin=7000
3dcarsizemax=8000
Change this numbers until you're satisfied. The smaller the number, the smaller the cursor.

If your desired car is not showing, you may did something wrong, copy the backup files and start over, step-by-step.

If you just want to go back to the original cursor with no car, delete all 5 files (4 X .mdl & 1 X .tex).

This is the place for me to THANK chas521 for showing me the light at the end of the tunnel.

Chas521 EDIT: To change the cursor in Primo, simply put an UNZIPPED folder into content\car.

you don't mention where we paste this file, the most important thing.

The edited file goes (UNZIPPED) in content\car as you could divert from the last line
Or do you mean the sys.txt? That's in the root.

Not that I want a car to download but the link in the OP does not appear to work no more.

Just saying like

Links fixed!

They downloaded great.......Thank You!!