1) the other component (de rol le shell or something) to make does not drop and is not obtainable. the only way to get de rol le shield is from black paper. drl shield is maybe 1 pd worth.
2) v502 is really really really overpowered. it gives 1.5x bonus to arrest/freeze/confuse and a 2x bonus to hell (v501 only has 1.5x bonus to hell). It literally doubles your chance to hell an enemy. In ultimate nothing really has less than 50 edk and hell has a 93% proc rate, so without v502 you have 93-50=43% chance to kill if hit, with v502 you have (93-50) x 2 = 86% chance to kill if hit. for more info on v502 and how it works with android's bonus to seize/arrest check out this post http://www.phantasystaronline.net/forum/index.php/topic/9827-ask-a-quick-question-get-a-quick-answer/?p=113561
3) red sword, p-arms blades, and g-assasin's sabers are all unreduced seize, the latter can use proof of sword saint for more ata. Holy ray is nice but has mst requirement so no androids, Arrest Raygun with 50h is a good weapon too. There is always s-rank j-cutter as well using sn glitch. If you are a human hunter then you really want arrest, so holy ray or arrest raygun, but an android hunter can use seize weapons very well due to cast bonus (link above shows comparison numbers with/without v502 for seize/arrest between humans/androids at 50 esp, basic grunt mobs have 10-30 and harder enemies have 50+).
4) Phonon Maser is in the Christmas Event, but it's just a novelty weapon it's really not that great. Drops from Barba Ray in that event.