The seal specification that you require should be 55x42x8mm R23 Viton double lip rotary shaft oil seal with gaiter spring. Have a look at the face of the seal to confirm this is the correct size as there is a possibility that another size could be used as well. This information is on the first page of the Alternative Parts List that is available via the MTWC website or the "M3W resources" sticky at the top of this forum list. You should be able to get this seal from a local supplier as it is a standard size but they are available from a company such as Bearing King in the UK if not, they cost about £12.
As you are a member of the MTWC you have full access to all the past Bulletin articles through the "Linked Bulletin Articles"
https://www.mtwc.co.uk/news-post/ . There is an article about doing this job dated March 2020. The MMC instructions are OK but I would suggest bolting the propshaft bracket rather than welding it as it will be easier to remove the propshaft another time. Also they make no mention of the need to put some silicon sealant on the splines of the input shaft to prevent oil leaking down them. The retaining nut is a lefthand thread. You will need to fabricate a gag to hold the flange when removing the LH thread nut, see photo in the article.
