Merge pull request #361 from aidancuckoo/patch-3

Update stm32f407vg_discovery.md

Author: makermelissa

_board/stm32f407vg_discovery.md

@@ -14,6 +14,13 @@ It includes an ST-LINK embedded debug tool, one ST-MEMS digital accelerometer, a
 
 ## Purchase
 * [ST](https://www.st.com/en/evaluation-tools/stm32f4discovery.html)
+* [Digi-Key](https://www.digikey.com/products/en?WT.z_cid=sp_497_0928_buynow&Enterprise=44&lang=en&Vendor=497&mpart=STM32F407G-DISC1)
+* [element14](https://nz.element14.com/stmicroelectronics/stm32f407g-disc1/dev-board-foundation-line-mcu/dp/2506840?ost=STM32F407G-DISC1&CMP=GRHS-1000962&ddkey=https%3ASearch)
+* [Future Electronics](https://www.futureelectronics.com/search/?selectedTab=products&q=STM32F407G-DISC1%3AmanufacturerName%3ASTMicroelectronics)
+* [Mouser](https://www.mouser.com/ProductDetail/STMicroelectronics/STM32F407G-DISC1?qs=sGAEpiMZZMu3sxpa5v1qrvO%2FQjIESWxJTP5oj%252Bcqf3k%3D)
+* [Newark](https://www.newark.com/stmicroelectronics/stm32f407g-disc1/dev-board-foundation-line-mcu/dp/72Y1168?st=STM32F407G-DISC1)
+* [RS Components](https://nz.rs-online.com/web/p/processor-microcontroller-development-kits/9107951/?relevancy-data=636F3D3126696E3D4931384E53656172636847656E65726963266C753D656E266D6D3D6D61746368616C6C7061727469616C26706D3D5E5B5C707B4C7D5C707B4E647D2D2C2F255C2E5D2B2426706F3D31313326736E3D592673723D2673743D4B4559574F52445F53494E474C455F414C5048415F4E554D455249432673633D592677633D4E4F4E45267573743D53544D333246343037472D4449534331267374613D53544D333246343037472D444953433126&searchHistory=%7B%22enabled%22%3Afalse%7D)
+* [Electronshik(website is in Russian)](https://www.electronshik.ru/item/ST/STM32F407G-DISC1)
 
 ## Contribute