You are welcome to visit the link below to request free samples of the thermal materials for testing. Each sample will include a strip of your chosen material with several labels in a size configuration that we have available. https://www.onlinelabels.com/samples Below are some similar sizes that we have available that match the specifications of the Zebra GK420D. If a custom size is required, we can create it for you. You can contact Customer Support at 888-575-2235 for more information or visit the following link, https://www.onlinelabels.com/special-order-custom-size-labels.aspx#rolls. https://www.onlinelabels.com/RL955DT.htm https://www.onlinelabels.com/RL961DT.htm https://www.onlinelabels.com/RL3647DT.htm