Sorry I'm too far away to offer my trailer, but I was also wary of tagging so I decided to do slap marking instead even though it's quite expensive to buy all the gubbins, but I'll need it every week now so a good investment really. My local abattoirs don't specify tags and they weren't registered stock.
I have always been on my own when loading/going to the abattoir and the first time I got myself in right old tizzy. The billy bonus with slap marking is that you can do it days or weeks in advance, so no last minute panic, whereas with tags I'd be concerned that they pull them out before the day if I did it too far ahead, and anyway I couldn't do that on my own lol.
The other thing I did was take the slap mark gear with me on the day, in case I hadn't done a very good job, I'm a worrier! But actually the abattoir had their own slap marker which they used if they weren't sure - my pigs had some black splotches in the wrong places! And I needn't have worried all the shoulders of pork came back with my herd mark perfectly visible

It's been plain sailing ever since

But if you decide to do it order the stuff now, might take a few days to come.