Although there are few fixed-blade production knives designed specifically for pikal, or RGEI, many existing models will suffice. Primary considerations, IMHO, would be a handle shape that is neutral, and a blade that is either straight or tending toward the wharncliffe shape.
Other possiblities might be Spyderco's Kumo and Temperance. Neither are designed specifically for pikal, but work very well in this style.
Ray Floro has marketed a cool variation of the Finnish pukko that has the cork-like handle "backwards," and they are extremely affordable.
Be advised that current advocates of pikal tend to prefer shorter blades, 4 1/2" or less. The fighting style is meant for bad-breath range. In these intimate encounters, the deployment of a longer blade can be easily fouled.
P.S.--chiron, welcome to these forums!