So that seller is essentially saying their plastic is better, so you won't have the problem - the REAL problem is not having the heat to begin with, rather than a Fuse that can withstand higher temperatures.
Fuses should NOT get hot!
Again, if it's getting hot, the source of that heat has nothing to do with the quality of the plastic, but to the quality of the connection between the blades of the Fuse and the sockets it sits in.
The sockets could be simply oxidized or they could be weak in their spring action, causing poor (high) contact resistance.
I don't know of anywhere to find the OEM Fuse Terminals, so the simplest solution is just to wire in a replacement external Fuse.
Note that Fuse carries pretty much all the load from the bike, which can include not only the headlights, but fuel pump, cooling fan, accessories connected to the OEM connectors.
The expended power dissipated by the Fuse comes from I^2 * R (Current Squared times Resistance)
The lower the resistance, the lower the dissipated power.
Also note that for any given resistance, the power is proportional to the square of the current.
Let's say the current is in the order of 20A - even if the contact resistance is only 0.01 ohms, then that still makes for 4W of power (equivalent to a parking bulb - and you know how warm that gets); if the resistance is higher, then the dissipated power rises accordingly.
So lower current will also mean that the expended heat will be less (you can't eliminate current, but you can make it go through an alternative bypass route e.g. headlight relay kit)
The other thing that can help is to lower the contact resistance - hence the proposed selection of the maxi-fuse, which has much bigger blade contact area (therefor inherently lower resistance than a physically smaller format)
Footnote: this is primarily only an issue with the classics - the Roadsters do not have the same configuration
(Touring do to some extent, but their current is less from the single headlight - on those bikes their weak link is the in-line connector from the battery - same problem, just a connector rather than a Fuse)
This was my fuse, not blown just melted away.
