The article “Photoionization Cross Sections of He and H2” published iopsciences has useful information regarding your quries about photoionisation cross section of singly excited Helium. This article can be accesses via the link
I am sure there are more recent and better documented photoionisation cross sections for the singly excited Helium. However since I struggled to find it, I post my finding here for anyone with a similar problem:
Article Photoionization from excited states of helium
In this paper the cross section is numerically calculated and given as a plotted function of the photoelectronenergy.