I suggest you start with this article:
https://www.ncbi.nlm.nih.gov/pubmed/15713727. You can download a free copy by following the link in the upper right of the PubMed screen.
Coviello, A.D., Matsumoto, A.M., Bremner, W.J., Herbst, K.L., Amory, J.K., Anawalt, B.D., Sutton, P.R., Wright, W.W., Brown, T.R., Yan, X., et al. (2005). Low-dose human chorionic gonadotropin maintains intratesticular testosterone in normal men with testosterone-induced gonadotropin suppression. J Clin Endocrinol Metab 90, 2595-2602.
Cliff notes in case you're not into reading endocrinology papers, the optimum dose appears to be around 1000 IU per week. Best to do this in split doses every 2-3 days. Also keep in mind that it takes about 6 weeks for sperm cells to fully mature, so what you do today doesn't appear in your ejaculate for up to 2 months.
Best of luck dad!