The last several times I've made pastry cream, I increased the amount of cornstarch and left out the wheat flour, so that it was gluten-free. Nobody noticed the difference. Last June I made a batch of gluten-free choux paste, so I had gluten-free eclairs, and they were very good. All I did was substitute a gluten-free flour mix for the wheat flour in the choux recipe I was using.
For a somewhat richer pastry cream, use two egg yolks instead of a whole egg. It's the yolk that thickens pastry cream. It also thickens a bit faster.
It was so funny Mike my daughter in law and I made the cream and went outside to wait for it to cool to put in the cream puffs and when we came back in the cream was gone and 3 young boys had smiles on their faces.