Just one of my recent projects with some extra ultra-capacitors I had.
Maxwell UltraCapacitors (x6 min, however I used 12 low grade\capacitance units from China through AliExpress)
https://www.tecategroup.com/store/index.php?main_page=product_info&products_id=1259 = Ultra caps (6 will do)
2.7V 3000F 2 String Super Capacitor Protection Board 5.4V Protection Board = Found on ebay (I didn't use them on the portable, but I use them on my other banks. I recommend them.
Connecting aluminum straps
Low-Z Strap, 12 pack, Maxwell Super Farad Ultra Capacitor BCAP0010 = Found on ebay (you can buy these or buy an aluminum strip from Home Depot and size\cut accordingly. That's what I do now, it's basically the same material, just cut neater.
Carlon 8 in. x 4 in. Junction Box in PVC = From Lowes or Home Depot (Essentially, get any box that will fit for you, I used this one due to the number and size of my caps from China, 12 caps that are smaller than the maxwells.)
Metal Handle - Found at Lowes or Home Depot
Mini DC 5-120V Voltmeter Blue LED Panel 3-Digital Display Voltage Meter 2-wire = Found on Ebay
2AWG wire with "Tin Coated Lugs" Do not use Copper. Copper and Aluminum don't mix.
TIN COATED BATTERY LUG, SOLAR, CAR, BOAT, WIND, RV, ELECTRICAL = Found on Ebay
Hope this helps.