You can buy travel adapters at various stores, both physical shops and online. Here are some options where you can find travel adapters:

1. Electronic stores: Stores like MediaMarkt, BCC, and Expert often have a range of travel adapters. You can visit the nearest store or check their website to view the selection.

2. Travel stores: Shops that specialize in travel essentials and accessories, such as the ANWB store, often sell travel adapters. Here, you can find different models and brands.

3. Online retailers: Popular online shops like Bol.com, Coolblue, Amazon, and Conrad offer a wide variety of travel adapters. You can visit the websites of these stores, select the desired type of travel adapter, and place an order.

4. Specialty shops: There are also specialty shops that focus on electronic accessories and adapters. These stores usually have an extensive selection of travel adapters. An example is the store ‘Reisstekkers.nl’, which specializes in travel adapters.

When purchasing a travel adapter, it is useful to consider the type of plug you need for the specific country or region you are traveling to. Also, check if the travel adapter is suitable for the voltage and frequency of the respective country. Read product descriptions and customer reviews to ensure you choose a suitable and reliable travel adapter.