Fish finder recomendations

[Scorpion61]

I just bought a 94 Stratos 201 pro XL. Onboard it has two what I assume are stock flashers built in. One in the front control consule and one in the drivers dashboard. Is there a proven and recomended replcement for this set-up? I have a hand held GPS I will use so depth/fish finders are all I need. I'm looking at either built-in or seperately mounted options.
Thankss in advance for any ideas anyone will share.