Yes, you can authorise someone else to collect the transaction pin on your behalf. However, the person can only do it at the LTA HQ at 10, Sin Ming Drive, Singapore 575701.
Do take note that the person must bring your Original NRIC as well as his/her own Original NRIC. If he/she does not have your Original NRIC, then he/she must have a Power of Attorney (POA) from you, and the original NRIC of the appointed attorney who must be also be physically present.
The Annexe A from LTA has the full information: https://www.onemotoring.com.sg/content/onemotoring/en/lta_information_guidelines/transaction_pin/documents_for_transaction/annex_a_and_b/_jcr_content/main_par/expandcollapse/par/download/file.res/Annex_A.pdf