DIY Jumper Suggestions

One benefit of bi-wiring is keeping the bass current separate from the more nuanced mids and highs.  If you run one of your bi-wire speaker cable pairs directly to the LF terminals and then jump the other pair between the MF and HF posts, then you probably don't need 8 awg wire.  If both pairs of your bi-wire speaker cables use the same gauge wire, then one option would be to match that gauge with your jumpers.  I would pick a type of wire that most closely matches what is in the speaker cables that you like, i.e., stranded or solid core, copper or silver, etc.

I like using a spade at one end and a banana at the other end of jumpers I have made so I do not need to stack spades.  I would not skimp on the connectors and if you purchase connectors that offer a set-screw  connection option, you can always use them again if you want to try different wire.  Furutech  FP-201 and FP-202 would get the job done.

IMO..... keep it simple to retain optimal synergy ...., full stop.

Go invest in the same brand / same model OEM factory jumpers 

Anything less is a full compromise with added unknown risks that you already know;  as evidenced by the existence of your post in the first place.

Dead soft .999 silver 8awg or 10awg round wire from Rio Grande on-line. No degradation associated with spades or solder joints. The 8awg has the right stiffness to hold a complete curve around the binding post.