LoopBack accessToken in invoked method observer

I have two LoopBack models, A and B. Part of their code is like this:

A.beforeRemote('create', function (ctx, unused, next) {
  ...
  B.findById(idForB, callBack);
  ...
});

B.observe('access', function (ctx, next) {
  const token = ctx.options && ctx.options.accessToken;
  const userId = token && token.userId;
  ctx.query = ctx.query ? ctx.query : {};
  ctx.query.where = ctx.query.where ? ctx.query.where : {};
  ctx.query.where.allowedUserId = userId;
});

Now, B's access observe hook has accessToken when REST calls are directly made from B/ API.

However, when making an API POST A/ API call, A's beforeRemote hook on create attempts to call B.findById which in turn triggers B's access observe hook, but in this scenario, there is no accessToken; not even option.

How do I propagate access information from A to B?

via Khan 'Sadh' Mostafa