Art Imitates Life
Lucky for you, the implantation (or rather reimplantation) of endocrine glands is already a thing. During parathyroidectomy, it is common practice to perform autotransplantation of a portion of the hyperactive tissue. This is usually done in the muscle tissue of the neck or forearm.
This is a whopping big parathyroid, much larger than the 3 to 5 mm "pebble" you're likely imagining (Moderator warning: Images contain blood and may be off-putting to some users):
Reimplantation is a simple matter of securing it to the muscle:
And Bob's your bloody uncle:
Muscle is already vascular and the new gland will rapidly grow its own vascular network. This location will not interfere with any other organs and the procedure is minimally invasive. The new gland will be protected by muscle and subcutaneous tissues and the reason why autotransplantation is done in the forearm is precisely for reasons of easy access. Any future access to your endocrine gland can be made under local anaesthesia.