This preprint presents a universal method to functionalize extracellular vesicles (EVs) by displaying ALFA nanobodies on their surface, letting any ALFA-tagged protein be attached as a modular adapter for targeting and imaging. Flow Induced Dispersion Analysis (FIDA) was used to characterize the binding of ALFA-tagged proteins to the nanobody-displaying EVs under physiological flow, confirming strong, specific binding and measuring the hydrodynamic radius of the vesicles (82 nm) and of the bound protein (3.4 nm). It is an example of using FIDA to quantify binding and particle size of extracellular vesicles and their cargo in solution.