There is not, but the reason for that is that there are many cases where the public vendor API isn't going to give you everything you might hope for. For instance, if they are selling race/class/level specific items, those items will almost certainly be wrong. The Public Vendor API is really meant to be queried for specific vendors, ones where you know that their inventory is never dependent on the specific character state, or where you are cherry picking for availability of specific items that wouldn't be restricted in such a manner. Due to technical limitations, we're unable to provide a truly public/"everything any character could theoretically get from this vendor right now" view, which would make switching to using the public vendor endpoint for a more generic use case difficult. It is something I would like to see come about someday, but there are technical limitations and difficulties in contextual content in place that makes the creation of such a service infeasible, at least with Destiny as it exists today.