I know where it is needed for a truck, so presume a bike needs it too. Below is what I had for a truck

Morocco you can use the green card.

Mauritania has its own policy you an buy at the border (from Western Sahara into Mauritania, or at diama or rosso bordering Senegal). I paid about 40usd for a 2 week policy which as a littel steep I thought but had just about had enough of the border officials and wanted to get away! Good thing I did get it there as police en route to St louis were pulling vehicles over and checking for insurance.

There is an ECOWAS policy which i think is underwritten by CEDEAO and covered me for the following countries:

Senegal, Mali, Burkina Faso, Ghana, Togo, Benin, and Nigeria. I think other countries like Cote Divoire and Gambia and Guinea were also on this policy but I didnt go there.

For this 6 month policy i got what i think was a great deal. 145 euros. Pretty fair i thought, esp as it was 23 seat capacity.

For Cameroon I had to get an seperate policy, which from memory cost me 60usd fo a month. Not obtainable at the border, had to get that when i hit the first sizeable town (Kumba I think).

For the other side of Africa, you can obtain the COMESA Yellow Card, which covered me for South Africa, Namibia, Botswana, Mozambique, Leshoto, Swaziland, Zimbabwe, Zambia, Tanzania, Kenya, Ethiopia....but ran out by the time I got to Sudan and Egypt so I bought additonal policies (similar prices to what i paid in West Africa). But from memory Sudan and Egypt were also both on this card. Though the dodgy Egyptians will still prob insist on a local policy.

So all in all should be noticably cheaper for a bike.