Is there a UCC code governing purchasing of customized products,
specifically the responsibility of the purchaser if they desire to
cancel a Purchase Order and thier responsibility to take the product
once it has been produced to thier specifications?

You should consult with an attorney as this is in no way legal advice,
nor should it be considered a substitute for such advice. This
information is here as a mere starting point for you and your attorney
from which you can begin discussing this matter.

UCC
§ 2-201
(1) Except as otherwise provided in this section a contract for the
sale of goods for the price of $500 or more is not enforceable by way
of action or defense unless there is some writing sufficient to
indicate that a contract for sale has been made between the parties
and signed by the party against whom enforcement is sought or by his
authorized agent or broker.  A writing is not insufficient because it
omits or incorrectly states a term agreed upon but the contract is not
enforceable under this paragraph beyond the quantity of goods shown in
such writing.

(2) Between merchants if within a reasonable time a writing in
confirmation of the contract and sufficient against the sender is
received and the party receiving it has reason to know its contents,
it satisfies the requirements of subsection (1) against such party
unless written notice of objection to its contents is given within 10
days after it is received.

(3) A contract which does not satisfy the requirements of subsection
(1) but which is valid in other respects is enforceable

(a) <i>if the goods are to be specially manufactured for the buyer and
are not suitable for sale to others in the ordinary course of the
seller's business and the seller, before notice of repudiation is
received and under circumstances which reasonably indicate that the
goods are for the buyer, has made either a substantial beginning of
their manufacture or commitments for their procurement</i>;