Depending on how old your panel is, they’ve come a long way, in terms of wattage and size, you may be able to fit 2 100W newer panels up there, I got 2 of these up on the roof from Renogy-
Renogy 100 Watt 12 Volt Eclipse Monocrystalline Solar Panel High Efficiency Module Off Grid PV Power for Battery Charging, Boat, Caravan, RV and Any Other Off Grid Applications
https://www.amazon.com/dp/B01B3TEM1E..._qEs9EbC1S51XS
They also make a slightly narrower panel too-
Renogy 100 Watt 12 Volt Monocrystalline Solar Panel, Compact Design 42.2 X 19.6 X 1.38 in, High Efficiency Module PV Power for Battery Charging Boat, Caravan, RV and Any Other Off Grid Applications
https://www.amazon.com/dp/B07GF5JY35..._eGs9EbNAG5BDD
I’ve also got one of their 100W suitcase panels without the controller that I have wired through the inboard controller, these are also available with their own controller-
Renogy 100W 12V Monocrystalline Off Grid Portable Foldable 2pcs 50W Solar Panel Suitcase Built-In Kickstand
https://www.amazon.com/dp/B00LXG4AXS..._5Ks9EbX6RR1BW
Also available w/without controller-
Renogy 100W Eclipse Lightweight Suitcase Without Controller, Panel Only, Black
https://www.amazon.com/dp/B07HN5R2KX..._zMs9Eb5YKEYRS
There’s a side port plug from Zamp and others that you can wire in to your existing controller and have as a plug in. I don’t think having 2 separate controllers connected to your battery works and make sure your current controller can handle whatever wattage you are throwing at it-
Zamp Solar Roof or Sidewall Solar Port, 10 Gauge Wire, Weather Resistant, 12-inch lead, Great for Portables or Roof Mounted Panels
https://www.amazon.com/dp/B00T36YVI4..._hzs9EbZZMZ7HY
Then get a length of 10G solar cable and put this onto the end as a plugin to the side port-
Nilight 10 Gauge 2 Pin Quick Disconnect Harness,Heavy Duty SAE Connector Bullet Lead Cable,2 Years Warranty
https://www.amazon.com/dp/B0057ZQJ12..._hCs9EbHME8K0P