Phycoerythrin-amino dextran/or something else conjenction

Hello,

we would like to conjugate Phycoerythrin to an amino dextran to create a custom intravascular contrast, together with FITC at the same time. Phycoerythrin has no NHS esters needed for this conjugation. If you have some experiences with alternative link (through crosslinking reagents, and how?) or other molecule with high molecule weight (Avidin?), please share them with us.
Many thanks in advance,
Best regards,
Martina Holicka, Czech Academy of Sciences