Seeking 2 German (T-Mobile) prepaid sim cards
 

Looking for 2 German prepaid SIM cards, preferably T-Mobile, standard size, but am willing to consider other providers.

In the past I have found USED cards plentiful on Ebay.de but don't see anything reasonable there. I have purchased 3 such cards and sold 2. This was several years ago.

I have found 900 coverage better than 1800 in the past -- the reason I would prefer T-Mobile.

The cards would be for my son and his wife traveling to Germany and other EU spots in the summer. We, too, are also traveling there this summer.

I used to have a SUNSIM card but they were bought out and then either went belly-up or the card expired, with credit.

you want it for voice or for data?
900 on T-Mobile is only 2G
for data on 3G all operator in germany use only 2100 MHz band,
LTE is 800 / 1800 and 2600 on T-Mobile.

LTE is inaccessible for T-Mobile's prepaid subscribers. Prepaid LTE is only available to eplus customers (including all of their MVNOs) and Vodafone CallYa customers who do subscribe to an LTE tariff option. As eplus' LTE coverage is quite limited, Vodafone is the only choice here.

By the way O2 and eplus have already opened up large parts of their 3G networks for biliteral national roaming which has significantly improved 3G coverage for customers of both former operators who have recently merged. The national roaming will be limited to 3G, so no chance for eplus subscribers to make use of O2's better LTE coverage. However O2 expects to have fully integrated both LTE networks by middle of 2016 by which time LTE may be activated for all kind of customers.