There are two types of front brake but I think our car only uses type "A".
Type " B" uses two bolts instead but I think the bolts are longer than the sliders on our type "A".
The guide pin with the Allen only has threads on the end of the pin and the rest is smooth to allow the caliper to slide along it.
It would probably be really hard to find an appropriate bolt with the correct dimensions.
You can get a set of Allen sockets from Harbour Freight for about $10.
I just went out and checked my guide pins and my parts car had an Allen hole where the 5 mm was too small and the 6 mm was too big and I don't have a 5.5 mm.
That didn't make sense to me so I checked my DD and it had a hex bolt head?
I know I bought my Allen sockets specifically for the brakes so I guess my new front calipers came with hex bolt slider pins instead of Allen?
Then I checked Rockauto and they have what you are looking for...