There is a service in Guadalajara that brings in shipments on a regular basis. I use it for anything shipping USPS since I do not trust MexPost to get me anything.
Te Lo Envio - https://www.teloenvio.mx/
You have the item shipped to their warehouse and they bring it in, generally within 1 - 2 weeks. They charge a 19% rate paid in pesos or USD when you pick the items up.
(no credit or debit cards). You still pay but it is significantly less than anything else I have found. Notifications on shipment status by e-mail. The name you register with must match the name you use as the shipping name, with their address located in McAllen.
If you are ordering large items, they can do special quotes as well, but thy are my go to service to avoid the high fees of FedEx, UPS, DHL.
Never had any issues.