Welcome aboard. This may be your first mod to the Monster but I can guarantee that it won't be your last!
If you like the design of the genuine DP indicators
but not the price (£80 per pair!), consider the Koso version, which appears to be an exact copy.
Louis Moto currently have them on offer at just £17.35 each
https://m.louis-moto.co.uk/artikel/k...ignal/10034004
Be aware that almost all aftermarket indicators will come with bullet connectors so, to wire them in, you'll either need to cut off the OE and bullet connectors and then solder the OE ones to the indicators or, alternatively, use an adaptor cable with a Ducati plug already attached e.g.
https://www.ebay.co.uk/itm/Adapter-C...-/124675555795
Check first whether you need to add resistors to get the correct flash rate. If you do, then get ones with the correct Ducati connectors and you won't then need the adaptor cables e.g.
https://www.ebay.co.uk/itm/Adapter-C...-/124699377524
I don't know whether the 821 needs resistors, the DP kit doesn't mention them. It may be that your ECU will accommodate the LED flashers automatically. Perhaps ask any 821/1200 owners on here who have done the swap whether they needed resistors.